The present invention relates to a process for refining amino acids. More particularly, it relates to a process for refining amino acids by using chelate resins having chelate groups which coordinate metal ions.
Amino acids are widely used for foods, feed, medicines, cosmetics and other commercial products.
Amino acids are produced by fermentation processes, synthesis processes or extraction processes. Crude amino acids produced by these processes are usually refined in order to obtain the desired amino acids for commercial uses by separating from raw materials and by-products, such as undesired amino acids contaminated in the crude amino acids.
The separation of the desired amino acids from the raw material or the by-products is generally conducted by a crystallization method utilizing the difference of solubilities. The crystallization method is usually conducted in aqueous solution, because solubility of amino acids in organic solvents usually used is small. However, repetition of the crystallization is needed in order to obtain the refined amino acid of high purity, since solubility of an amino acid is often very close to that of the other amino acid in aqueous solution. This makes the operation complicated. Furthermore, the crystallization method is hardly applied to for separation of, for example, leucine from isoleucine,structure isomer thereof. The third components such as .beta.-naphthalene sulfonic acid or 2-bromo-5-toluene sulfonic acid are added to the amino acids to form salts of the respective amino acids, and then one salt is separated from another salt by taking advantage of the difference of respective solubilities (Fine Chemical, Mar. 15, 1982, page 10). Accordingly, lots of time and many equipments and apparatuses are needed for refining amino acids. Equipment cost and running cost are very large.
Under the circumstances, the inventors have made extensive study to find an efficient process for refining amino acids. As the result, the inventors succeeded in establishment of the present invention.